Based on seismic data, exploration and appraisal drilling and the development of the reservoir, production wells are positioned and drilled. Normally the development and production of an oil and gas field implies drilling several wells at different stages to obtain good drainage of the reservoir.

When production well(s) are completed and all production equipment is installed, tested and approved the production may commence.

Oil and gas exploration and production is divided into two main categories; onshore and offshore fields. The main differences are the environment, the equipment used and the logistics. Drilling and production of offshore oil and gas fields are in most cases more complex than for drilling and production of onshore fields. However the principles of finding and draining the reservoirs are the same.

Field development and planning
The planning stage is a demanding stage since normally there will be a desire for high speed to shorten the time from discovery to actual production to minimize the time before the cash flow is positive. However, in many cases the time span is significant (years even decades) between discovery and detection of hydrocarbon resources until field development and production. This is in most cases due to uncertainties related to potential production volumes, technical challenges and cost.

Main elements of field development planning:

• Drainage strategy, concept evaluation and decision
• Deciding how many wells (production wells, injection wells and wastage wells) that need to be drilled to produce the oil or gas.
• Deciding the s´design of the production wells
• Deciding the concept for the production facilities
• Deciding the export route for for the crude oil or gas

Plan for development and operation (PDO)
In most regions where oil and gas is discovered and produced it is required by local authototies that some sort of plan addressing all aspects of the field development and utilization is submitted and approved before field development can start or at least before any physical activities at the location may be started.